Treatment of hydrocarbons



:Marel-726, 1946. D.' c. WALSH, JR?, ErAL, '2,397,224

, Y Y'1;'REATMEN1 oF HYDRoARBQNs n Filed Dec. 2, 1943 Stripper Mixtur;from lsomenzanon Reactor Mixu re from Alkylufion Reactor Fresh CousicASpentn ,4

Caustic l 4 N-Puruffin 'IN1/mimics.

JMA/94M y l .51??@6' ATTORNEY.l

Patented Mar. 26, 1946 TREATMENT F HYDROCARBONS l David C. Walsh, Jr.,and Elza. Q.l Camp, Goose Creek, Tex., assignors to Standard OilDevelopment Company, a corporation of Delaware Application December 2,1943, Serial No. 512,582

7 Claims.

The present invention is concerned with a method for treating reactionproducts from catalytic conversion processes for removal of acidicmaterial which cause corrosion on distillation of the reaction products.More particularly, the in-- vention is concerned with the treatment withalkaline reagents of products resulting from the alkylation ofisoparafiins with olens and the isomerization of normal parain whenacid-reacting materials are employed to catalyze these reactions.

In alkylation of isoparains with olens, especially when concentratedsulfuric acid is employed to catalyze the reaction, there are formedalkyl sulfates which are soluble to some extent in the hydrocarbonproduct of the reaction. vSome of the'olenic charge to the alkylationrclaction isunreacted and, consequently, also leaves the reaction systemin the hydrocarbons. 'Besides these contaminants the'hydrocarbon productfrom the alkylation reaction has also been found to contain some SO2.The alkyl sulfates resulting from the reaction havebeen observed tobreak down at the temperatures of distillation of the product to formcorrosive materials.

In the isomerization processes employing metal halides. as catalystsAand promoted by hydrogen halides the product has been found to containappreciable quantities of both the metal halides and the hydrogenhalides. The hydrogen halide is easily recoverable iromthehydrocarbonproduct by distillation, and it is economically desirable to recover thehydrogen halide promoter in the isomerization process. The metal halidedue to its volatilizable nature is carried over from the isomerizationreactor with the isomerized product and its recovery for reuse orremoval poses a considerable problem. This carry-over of volatilizablemetal halide is undesirable since the yvolatilizable metal halide oncooling of the hydrocarbon product condenses and solidifiesin theauxiliary equipment usually associated with isomerization reactions.Thus the auxiliary equipment, such as condensers, coolers andfractionating towers, ultimately become plugged with the deposited metalhalide. Furthermore, the carryout of the volatilizable metal halideresults in a condition which ultimately will causefthe equipment to beimpaired by corrosion to the extent that it no longer can be utilized.

Most isomerization and alkylation processes are operated in conjunctionwith each other. Thus the alkylation process requires isoparailins forreaction with the olefins and the isomerization process is employed toproduce the isoparains. It is often desirable to utilize onedistillation system for processing of the reaction products fro-1n thetwo operations. In many cases it is desirable to combine the reactionproduct from the isomerization reaction with the reaction product fromthe alkylation reaction, free them from acidic reaction products, andthen to distillthem in one distillation system as mentioned.

However, when the reaction products from Lan isomerization andalkylation process employing, respectively, aluminum chloride and'ysulfuric acid as catalysts, were combined, causticand .water Washed, andsubsequentlyv distilled, it wasfound that'the distillation equipmentsuffered 'aac'onsiderable amount of corrosion clue'to aci'di'cfmaterialbeing formed at thetemperaturesemploye'd in the distillation system. It'was established that the corrosive materials being formedwere producedas a result 'of decomposition of 'acidic forming bodies that were notfremove'd infthe caustic and water `washing step mentioned before. Itis, therefore, the main objectrof the present invention to provide aprocesswhereby the` hydrocarbon reaction productsfrom an :alkylation andisomerization process, employingfrespectively, aluminum chloride fandsulfuric a'c'id yasfc'atalyst, may be treated Iwith analkalinereagentLand distilled vwithout corrosion of =th`e distillationequipment.

In the present invention .formation'ofreaction products which decomposeat the temperatures employed in the distillation step of this process isprevented 4by treating the combined isomerizerl and alkylated productwith'alkaline reagents iin a particular and 'critical sequence of-steps.This particular series of steps includes treatmentfof the isomerizedproduct acontaining the dissolved metal halide `with an alkaline reagentvpriorfto mixing lwith the alkylated product. The 'combined streams arethen subjected to further treatment vwith alkaline reagent,` thealkalinereagent removed and the Vhydrocarbon mixture subjected to distillation.When operating in accordance with the present invention the distillationequipment is not affected, and the hydrocarbonfractions from thedistillation equipment are :found to be free of the materials whichordinarily cause corrosion.

The reason for the unexpected 'resultzachieved by operating inaccordancewith the `present invention is not completely understood, butit` is believed that in the conventional operation the aluminum chlorideand hydrogen chlorideprometer contained in the isomerization `productstream react with, alkyl suliates and/or'residual unsaturatedhydrocarbonsremaining in the alkylated product. It is believedA thatthese reaction products are organic halides and in the present case theyare believed to be alkyl halides. When a stream containing these organicchlorides was subjected to the temperature. encountered in thedistillation of the alkylate-containing stream they vsuiereddecomposition reactions whereby hydrochloric acid andLsuliur .dioxidewere released, which, in conjunction With'water usually associated withthese streams, caused" an extremely corrosive condition to exist in theoverhead distillationV equipment.

VFor a more specic description of the present invention reference ismade to the single figure,

not shown herein since this separation doesv not n which is adiagrammatic now plan of one embodiment according to the invention.

Referring t the'drawing in detail, numeral II designates a ow linecarrying isomerization product from an isomerizationreactor inwhich aparaln hydrocarbon is isomerized in the presence of a promoter and avolatilizable metal halide Y The isomerized product Vin line I'I Yisinjected thereby into fractionator deposited on a carrier.

I2, which in the present case is a distillation towerin which aseparation is made'between the` hydrocarbons and the metal halide.Thercon'ditions of fractionator I2 are such that only a crude separationbetween the hydrocarbon and the metal halide is made; Thus only asuflicient e amount of reux is introduced to fractionator V'I2fso thatVthe metal halide remains as a bottoms fraction in the fractionator,amounting to between' 2 and 20% of the isomerized product introducedthereto by line II A more complete description of the function offractionator I2 will be'found in pending application, U. S. Se-

IialLNO.V488,124, fJledMay 24, 1943, for William "lqliranlrlin, Theprocessdescribed and claimedA in the aforementioned application does notform a part of this invention, but the present invention maybe moreeasily understood by reference tothe fractionator I2. j c

Ordinarily in the aforementioned pending application the metal lhalideremaining Vas af biot-V ltoms fraction in'the fractioator I2 is recycledi to the isomerization reactor.Y ',However, quite fre- Y Vquently themetal halide fraction becomes fouled with heavy hydrocarbons and tarryreaction products which make it unsuitable for return to the l"isomerization. reactor as described in TJ. S. Se-

rial No.' 488,124. *residuali-liquid Ycontains undesirable components Itis in the cases when'the forlinclusion in theisomerization reactor that:the Ypresent invention is practiced in conjunction with fractionatorI2. Y,

fied product is carried by line I6 Yto a hydrogen chloride stripper I'I.Line i6 is provided with a` .branch line I8, controlled by'valve I9,which per- 'mits the return of a selected amount of the liqueed productto the top of iractionator I2 to pass downwardly countercurrently toVthe vaporous Y product ascending therein.V A liqueed residue Zy whichcontains substantially all of theV metal halide contained in theisomerized product, forms at the bottom` ofV fractionator I2V anddischarges therefrom -by line 2i tobefhandled, as will be` describedfurther. ,i

The liquefied productY from accumulator I5Y `passes-by line I6 andbranchline22, to hydrogen'chloride stripper Il Which is provided withvheating meansV 23` for adjustment Yof tempera- -V ture therein, Whileuncondensed gases are re-` -moved through line til. Conditions inhydrogen chloride stripper I1 are such that hydrogen chloride and lighthydrocarbons are removed there- Afrom by way of line 26; YSeparationbetween the` hydrogen chloride andthe vlight hydrocarbons is` form partof the present invention. In anyevent the hydrogen chloride afterseparation from the light hydrocarbonsY may be recycledjto'theisomerization stage from Which the isomerized product in line I Ioriginates. The .isomerized product,v

substantially free from hydrogen chloride, dis-- charges from hydrogenchloride stripper Il byV Way of lines and 25 for furtherdistillationforv I separation of the isoparailin from the normal parain;Y Y

The liquefied residue 2B, withdrawn-from fractionator I2 by Way ofY line2l, discharges into line 2'I where it is intermingled with an alkalinereagent. The mixture of alkaline reagent, metal halide and hydrocarbonsfrom lines 2I- and 21 are intimately contacted in mixing means 28 anddischarged therefrom by way of line 29 to which is introduced, by way ofline 3i), an alkylated product resulting from the alkylation of anisoparaflin with an olen in the presence ofgstrong Y The mixture ofisomerized product, alkaline reagentY and alkyl- 'Y sulfuric acid as thecatalyst.

ated product is then further treated by addition' of additionalamountsof alkaline reagentV through Yline 3|. The combined streams Athen passtoV mixing device 32 in which the mixture is intimately contacted andpasses thence by Way i of line 33 to settler 3d which is of sulcientcapacity Vto allow separation by gravity between 'a the hydrocarbon andalkaline phases. AftertheY hydrocarbons have separated from the alkalinereagent, they are withdrawn from settler 34 by Way of line 35 and areintroduced thereby intoxY ractionator 36 which is provided with heatingmeans 3l for adjustment of temperature and, pressure conditions.

. Fractionator 35, it is understood, may lcomprise one ormoredistillation'towers as desired. In this particular instance fractionatorA36 is shown to Y be a single distillation tower with line 38forwithdrawal of isoparain as an overhead fraction, line 39 forsegregation of a normal parailn fraction as a side stream and line 40for withdrawal ofranV alkylate stream as a bottoms fraction.

It is in fractionator 36 and liriosV 38,VY Strand/45'.

that the corrosion troubles mentioned'hereinbe-A fore were encounteredwhen operating according n a to conventional practice. tionV theVcorrosion avoided.V f

The alkaline kphase separated in settler 34 discharges ktherefrom byWay. ofline 4I andis` in- In the present finvenjected by pump d2 intoline 2'!V whereby the rev sidual liquid from fractionator Line El Yisprovided with a branch line 43, con- I2 is treated.

trolled by valve 44, whereby a portion, or all,.of

Y the alkaline reagent Withdrawn by lineu 4I from settler 3c may bediverted to treatV the mixture in line 29. `Preferably, however, thealkalinereagent withdrawn from settler 34 is employed to treat theresidual liquid 2Q from fracticnator-I in the manner described. L

From timeto time kthe alkalinereagentwithdrawn from settler 34 by line Mwill be decreased Y in alkalinity to a pointwhere it nolonger func- Ytions eiectively in removing acidic materials from the streams flowingthrough lines 29 and 30. `In

those cases a portion of the .alkaline reagent is discarded` from thesystem through line i5 b opening valve t6 locatedtherein.

When spent alkaline reagent isdiscarded from the systemthrough line 3Enit will be necessary to add an amount of fresh alkaline reagent tomaintain the strength at the optimum level. VThis diflicultiesY aresubstantially' can be accomplished by either of two ways. Thus freshalkaline reagent may be introduced into either line 21 or line 29 byopening either valve 41 in line 21 or valve 48 in line 3 I, the freshalkaline reagent being introduced from a source not shown by way of line49.

As an alternate method of operation, in some particular cases it may bedesirable to bypass completely fractio-nator l2. In these instancesValve 50 in line Il will be closed and valve 5| in line 52 will beopened, and the isomerized product delivered directly to hydrogenchloride stripper I1 without the preliminary fractionation forconcentration of metal halide. When operating in accordance with thealternate method, valve 53 in line 25 is closed and valve 54 in line 55opened allowing delivery of the hydrogen chloride stripped hydrocarbonsto line 2|. Thereafter the operation is substantially as described inthe preferred embodiment.

It is obvious to the skilled Worker that the alternate operationrequires processing of larger quantities of hydrocarbon than in thepreferred embodiment.

The seriousness of the problem solved by the present invention will beillustrated by the analysis of the water condensed with the overheadstream from fractionator 36 prior to operating in accordance with themethod described herein. When the residual liquid from fractionator I2was mixed with the alkylated product introduced by line into themixture'and caustic washed, the water condensed with the overhead streamfrom fractionator 36 had a pH of 3.2 and contained about 17,000 P. P. M.of chlorides, which is an extremely corrosive condition. When operatingin accordance with the present invention with the dual-caustic treatingstep and with careful control of the amount of caustic used, the watercondensed with the overhead stream contained a negligible amount ofchlorides and had a high pH value. Analysis of the alkylate dischargedby way of line 40 when operating in accordance with the presentinvention showed only traces of organic chloride.

The amount of caustic employed to treat the residual liquid 20 fromfractionator l2 will vary depending upon the strength of alkalinereagent employed and the amount `of residual liquid formed. However,with a residual liquid from fractionator l2 amounting to 500 gallons.per hour good results were obtained with a total alkaline treat ofbetween 4,000 and 5,000 gallons per hour of alkaline reagent of about 10B., which in this case wasa sodium hydroxide solution. It will beobvious to the perso-ns skilled in the art that the amount of alkalinereagent employed may vary widely. It is good practice to employ asuicient amount of alkaline reagent to neutralize completely the acidityin both the isomerized and alkylated product streams.

The nature and objects of the present invention having been fullydescribed and illustrated, what we wish to claim as new and useful andto secure by Letters Patent isi 1. In a process for the treatment withan alkali metal hydroxide of the combined product from an isomerizationstage and an alkylation stage in which the isomerization stage iscatalyzed with a metal halide and the alkylation stage is catalyzed witha mineral acid the steps of admixing product from the isomerizationstage with a solution of an alkali metal hydroxide, adding alkylatedproduct to the mixture oi a solution of an alkali metal hydroxide andisomerized product, treating the resulting mixture with additionalamounts of a solution of an alkali metal hydroxide, settling to obtain ahydrocarbon phase and distilling the resulting hydrocarbon phase.

2. In a process for the treatment with a solution of an alkali metalhydroxide of the combined product from an isomerization and alkylationprocess in which the isomerization stage is catalyzed with a metalhalide and the alkylation stage of the process is catalyzed with astrong mineral acid the steps of subjecting isomerized product to adistillation to obtain a fraction in which the metal halide isconcentrated, treating the metal halide-containing fraction with asolution of an alkali metal hydroxide, adding to the resulting mixturealkylated product, subjecting the resulting mixture to treatment withadditional amounts of a solution of an alkali metal hydroxide, settlingthe treated mixture of isomerized and alkylated product to obtainalkaline and hydrocarbon layers, separating the alkaline layer from thehydrocarbon layer, and distilling the hydrocarbon layer.

3. A process in accordance with claim 2 in which the separated alkalinelayer is employed to treat the metal halide-containing fraction.

4. A process in accordance with claim 2 in which the separated alkalinelayer is divided into two portions, one is added to the metalhalide-containing fraction and the other to the mixture of treated metalhalide-containing fraction and alkylate.

5. In a process for treating the combined products from an isomerizationand alkylation process in which the isomerization is vcatalyzed byaluminum chloride and the alkylation by strong sulfuric acid whereby theproducts are recovered free from inorganic and organic chlorides thesteps of distilling the product from the isomerization to obtain aconcentrate of metal halide in hydrocarbons, treating the concentrate awith a caustic reagent, admixing the treated concentrate with productfrom the alkylation, subjecting the resulting mixture to treatment withadditional amounts of alkaline reagent, set-l tling the treated mixtureto obtain hydrocarbon and caustic'reagent phases, withdrawing the4caustic reagent phase and distilling the hydrocarbon phase to obtainproducts substantially free of chlorides.

6. A process in accordance with claim 5 in which the caustic phase isemployed to treat the metal halide concentrate.

'1. In a process for the treatment with a solution of an alkali metalhydroxide of the combined pr-oduct from an isomerization and analkylation process in which the isomerization stage is catalyzed with ametal halide and the alkylation of hydrocarbons in an alkylation stageis catalyzed with a mineral acid, the steps of treating product from theisomerization stage with a solution of an alkali metal hydroxide, addingproduct from the alkylati-on stage to the treated isomerization productto form an admixture, treating the resulting admixture with a solutionof an alkali metal hydroxide and subsequently distilling to separate ahydrocarbon fraction.

DAVID C. WALSH, JR. ELZA Q. CAMP.

